Short wave-long wave receiver



Feb. 18, 1936. J. ROHNFELD SHORT WAVE-LONG WAVE RECEIVER Filed Feb. 1'7,1933 JO/M/V/V 7 I ATTORNEY Patented Feb. 18, 1936 UNITED STATES SHORTWAVE-LONG WAVE RECEIVER Johannes Rohnfeld, Berlin, Germany, assignor toTelefunken Gesellschaft fur Drahtlose Telegraphic in. b. H., Berlin,Germany, a corporation of Germany Application February 17, 1933, SerialNo. 657,157 In Germany May 28, 1932 3 Claims.

The present invention relates to a heterodyne receiver for the receptionat will of short-waves, ultra-short and normal broadcast waves.

As a result of the increasingly more extensive 5 use of short andultra-short waves in broadcasting, side by side with the wave-lengthband heretofore mostly customary between 200 and 2000 meters, the demandhas arisen to render standard broadcast receiver sets useful also forshort-wave work. This end is attainable by the use of auxiliary meansconsisting of a short-wave heterodyne receiver stage. The normalbroadcast receiver, then, constitutes the amplifier and rectifier forthe ensuing intermediate frequency.

5 Now, in what follows certain circuit schemes shall be disclosed whichare adapted to insure the change, with the combination receiver(auxiliary stage and standard receiver) in a particularly simple andpractical manner from the reception of short waves to the reception ofstandard broadcast bands.

One embodiment is shown, by way of example, in the figure where Adesignates the short-wave accessory (adapter) device comprising anoscillator and mixing tube I, the latter being a double grid tube. Bdenotes the intermediate frequency amplifier, including tube 2, which isa standard broadcast receiver set. Whenever short waves shall bereceived, switch S is shifted over into contact k. In that case, thetwin-grid tube I receives direct current energy from the plate-potentialsource Q and operates as an oscillator. The aerial is then connected byway of the small condenser c with the other grid of the twin-grid tubeso that it works as a radio frequency amplifier and modulator, theensuing intermediate frequency being thereupon further amplified in thecustomary Way in the intermediate frequency amplifier B.

If broadcasting stations sending on the usual wave bands are to bereceived, all that is necessary is to position switch S on the contactn. In this case the aerial is connected directly with the broadcastamplifier tube 2, while the oscillator at the same time ceases tooscillate since its plate direct current circuit is broken. While thecowpling between the aerial and the short-wave accessory device(adapter) remains in existence, the condenser 0 represents a very highimpedance for standard broadcast waves. Condenser K blocks the antennafor direct current, while for radio frequency energies it constitutes ashort-circuit.

While I have indicated and described one system for carrying myinvention into effect, it will be 7 apparent to one skilled in the artthat my invention is by no means limited to the particular organizationshown and described, but that many modifications may be made withoutdeparting from the scope of my invention as set forth in the appendedclaims.

What is claimed is:

1. In combination with a radio receiver having a resonant input circuitadapted to be tuned to a desired radio frequency of the broadcast bandand a signal collector, a short wave adapter unit 5 comprising a tubehaving a resonant circuit connected between its cathode and a gridelectrode, the resonant circuit being tunable over a desired short waverange, means coupling the signal collector to said resonant circuit,.asecond resonant 10 circuit connected between the cathode and a gridelectrode of said tube, a source of direct current potential for theoutput electrode of said adapter tube, means for regeneratively couplingthe output electrode to the said second resonant 15 circuit, and meansconnected to said source and receiver input circuit, arranged forselective connection tosaid adapter tube output electrode or said signalcollector.

2. In combination with a radio receiver having 0 a resonant inputcircuit adapted to be tuned to a desired radio frequency and a signalcollector, a short wave adapter unit comprising a tube having a resonantcircuit connected between its input electrodes, the resonant circuitbeing tunable over a desired short wave range, condenser means having ahigh impedance to frequencies to which said receiver input circuit istuned coupling the signal collector to the short wave tunable circuit, asource of direct current potential for the output 30 electrode of saidadapter tube, means comprising a local oscillator, connections forimpressing oscillations from said oscillator on said tube, said meansand said connections being independent of said resonant circuit, andmeans, connected to 35 said source and receiver input circuit, arrangedfor selective connection to said adapter tube output electrode or saidsignal collector.

3. In combination with a radio receiver having a resonant input circuitadapted to be tuned to a 40 desired radio frequency and a signalcollector, a short wave adapter unit comprising a multi-grid tube havinga resonant circuit connected between its cathode and one of its gridelectrodes, the resonant circuit being tunable over a desired short 45wave range, means coupling the signal collector to the short wavetunable circuit, a source of direct current potential for the outputelectrode of said adapter tube, a second resonant circuit connectedbetween the cathode of said tube and an- 50 other of its grids, meansfor regeneratively coupling the output electrode to the said secondresonant circuit to form a local oscillator, means connected to saidsource and receiver input circuit, arranged for selective connection tosaid adapter 55 tube output electrode or said signal collector, and adirect current blocking condenser connected between the signal collectorand said direct current potential source.

JOHANNES ROI-INFELD. 50

